Ethylene‐octene copolymers prepared by Dow's INSITE™ constrained geometry catalyst technology present a broad range of solid‐state structures from highly crystalline, lamellar morphologies to the granular morphology of low crystallinity copolymers. As the comonomer content increases, the accompanying tensile behavior changes from necking and cold drawing typical of a semicrystalline thermoplastic to uniform drawing and high recovery characteristic of an elastomer. Although changes in morphological features and tensile properties occur gradually with increasing comonomer content, the combined body of observations from melting behavior, morphology, dynamic mechanical response, yielding, and large‐scale deformation suggest a classification scheme with four distinct categories. Materials with densities higher than 0.93 g/cc, type IV, exhibit a lamellar morphology with well‐developed spherulitic superstructure. Type III polymers with densities between 0.93 and 0.91 g/cc have thinner lamellae and smaller spherulites. Type II materials with densities between 0.91 and 0.89 g/cc have a mixed morphology of small lamellae and bundled crystals. These materials can form very small spherulites. Type I copolymers with densities less than 0.89 g/cc have no lamellae or spherulites. Fringed micellar or bundled crystals are inferred from the low degree of crystallinity, the low melting temperature, and the granular, nonlamellar morphology. © 1996 John Wiley & Sons, Inc.

SYNOPSISDifferential scanning calorimetry (DSC) was used to analyze the crystal distribution in homogeneous ethylene-octene copolymers polymerized by the constrained geometry catalyst technology (CGCT). To minimize ambiguities from thermal history effects, copolymers were isothermally annealed at temperatures within the melting range. The cumulative crystallinity was related to the crystal distribution by the Gibbs-Thomson equation. The results provided a clear distinction between Type I copolymers (density less than 0.89 g/ cc) and Type I1 copolymers (densities between 0.89 and 0.91 g/cc). The former had a singlecrystal population that was identified with the bundled crystals seen in transmission electron micrographs. In comparison, the latter had two crystal populations that correlated with lamellar crystals and bundled crystals. 0 1995 John Wiley & Sons, Inc.

SYNOPSISEthylene-octene copolymers prepared by Dow's INSITETM constrained geometry catalyst technology present a broad range of solid-state structures from highly crystalline, lamellar morphologies to the granular morphology of low crystallinity copolymers. As the comonomer content increases, the accompanying tensile behavior changes from necking and cold drawing typical of a semicrystalline thermoplastic to uniform drawing and high recovery characteristic of a n elastomer. Although changes in morphological features and tensile properties occur gradually with increasing comonomer content, the combined body of observations from melting behavior, morphology, dynamic mechanical response, yielding, and largescale deformation suggest a classification scheme with four distinct categories. Materials with densities higher than 0.93 g/cc, type IV, exhibit a lamellar morphology with welldeveloped spherulitic superstructure. Type I11 polymers with densities between 0.93 and 0.91 g/cc have thinner lamellae and smaller spherulites. Type I1 materials with densities between 0.91 and 0.89 g/cc have a mixed morphology of small lamellae and bundled crystals.These materials can form very small spherulites. Type I copolymers with densities less than 0.89 g/cc have no lamellae or spherulites. Fringed micellar or bundled crystals are inferred from the low degree of crystallinity, the low melting temperature, and the granular, nonlamellar morphology. 0 1996 John Wiley & Sons, Inc.

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